JavaScript提升函数与函数变量 [英] JavaScript hoisting function vs function variable

问题描述

这是我的javascript代码：

Here is my javascript code :

    console.log(a);
    c();
    b();            
    var a = 'Hello World';
    var b = function(){
        console.log("B is called");
    }
    function c(){
        console.log("C is called");
    }

现在输出：

undefined
hoisting.html:12 C is called
hoisting.html:6 Uncaught TypeError: b is not a function

我的问题是关于为什么c（）和b（）表现不同。并且b应该抛出类似b未定义的错误。

My question is regarding why c() and b() behaving differently. And b should throw error something like b is not defined.

推荐答案

功能声明将与其正文一起提升。

函数表达式不会，只会挂起var语句。

---

这是你的代码在编译时之后看起来对解释器的看法 - 在运行时之前：

A Function Declaration will be hoisted along with its body.

A Function Expression not, only the var statement will be hoisted.

---

This is how your code "looks" like to the interpreter after compiletime - before runtime:

 var c = function c(){
      console.log("C is called");
 }

 var a = undefined
 var b = undefined

 console.log(a); // undefined at this point
 c(); // can be called since it has been hoisted completely
 b(); // undefined at this point (error)

 a = 'Hello World';
 b = function(){
     console.log("B is called");
 }

KISSJavaScript

KISSJavaScript

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